The overall objective of this proposal is to examine the biochemical and morphological response of the testis and epididymis to withdrawal of either FSH or LH without reporting to hypophysectomy. This is achieved by the use of a relatively new, simple and elegant tool, namely antigonadotropic sera. Potent antiserum to purified rat FSH has been prepared, made monospecific by suitable absorption and shown to neutralize biologic activity of rat FSH in bioassay systems. It is proposed to examine the effects of neutralizing FSH on the morphology of the Sertoli cell, production of androgen binding protein (ABP) by Sertoli cells, hence sperm maturation in the epididymis and fertility. Androgen levels in plasma and rete testis fluid, and plasma LH levels will be examined. A potent antiserum to purified sheep LH has been prepared, shown to cross-react with rat LH and neutralize its biologic activity in bioassay systems. The effects of neutralizing LH activity on structure of Sertoli cells and Leydig cells, androgen levels in plasma and rete-testis fluid, and plasma FSH levels will be investigated. The importance and indeed the necessity of ABP in spermatogenesis and sperm maturation is not clear. If ABP is essential for normal male fertility, then all methods to selectively inhibit ABP need to be investigated. Since ABP production by Sertoli cells is controlled by FSH of neutralizing antiserum of FSH should provide important new experimental data concerning the response of the Sertoli cell to selective withdrawal of FSH, both at the ultrastructural and biochemical level. While we are not suggesting the use of antisera as a method of contraception, this type of experimentation is essential in view of the likelikhood that inhibin may soon be characterized and used to pharmacologically interrupt FSH, selectively. The importance of our approach lies in the fact that this offers a method of selectively decreasing FSH levels without affecting circulating testosterone levels.